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digitalmars.D - circular deps

reply Scott <bob zone.com> writes:
Hi all,

Whats the correct way to use imports to handle the following type of circular
dependency?

//main.d --------------8<---------------
import vec3, mat3, quat;
int main() { return 0; }

// mat3.d--------------8<---------------
module mat3;
import vec3, quat;
struct Mat3 { Vec3[3] m; }

// quat.d--------------8<---------------
module quat;
import vec3, mat3;
struct Quat {}

// vec3.d--------------8<---------------
module vec3;
import mat3, quat;
struct Vec3 { }


I get this back from the compiler....

unixbox$ dmd main.d vec3.d mat3.d quat.d 
vec3.d(6): struct vec3.Vec3 no size yet for forward reference
vec3.d(6): struct vec3.Vec3 no size yet for forward reference
vec3.d(6): struct vec3.Vec3 no size yet for forward reference
unixbox$

Thanks
S
May 17 2007
next sibling parent reply "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"Scott" <bob zone.com> wrote in message 
news:f2houk$2l1a$1 digitalmars.com...

 Hi all,

 Whats the correct way to use imports to handle the following type of 
 circular dependency?

 //main.d --------------8<---------------
 import vec3, mat3, quat;
 int main() { return 0; }

 // mat3.d--------------8<---------------
 module mat3;
 import vec3, quat;
 struct Mat3 { Vec3[3] m; }

 // quat.d--------------8<---------------
 module quat;
 import vec3, mat3;
 struct Quat {}

 // vec3.d--------------8<---------------
 module vec3;
 import mat3, quat;
 struct Vec3 { }


 I get this back from the compiler....

 unixbox$ dmd main.d vec3.d mat3.d quat.d
 vec3.d(6): struct vec3.Vec3 no size yet for forward reference
 vec3.d(6): struct vec3.Vec3 no size yet for forward reference
 vec3.d(6): struct vec3.Vec3 no size yet for forward reference
 unixbox$


I would imagine that you have more code (so for example, vec3 really does 
depend on mat3 and quat).  As far as I'm concerned, this is a bug in the 
compiler that Walter has never been particularly intent on fixing.  I've 
always ended up just clumping any circularly-dependent modules into one 
file, even if it doesn't really make sense to.  Makes the compiler shut up.
May 17 2007
parent Scott <bob zone.com> writes:
Yeah, this is the code stripped down to its most minimal form that still causes
the compiler to barf.

If someone can tell me for sure that this is a compiler bug, I'll have a go at
fixing it myself.

Cheers
S

Jarrett Billingsley Wrote:

 I would imagine that you have more code (so for example, vec3 really does 
 depend on mat3 and quat).  As far as I'm concerned, this is a bug in the 
 compiler that Walter has never been particularly intent on fixing.  I've 
 always ended up just clumping any circularly-dependent modules into one 
 file, even if it doesn't really make sense to.  Makes the compiler shut up.
May 18 2007
prev sibling parent Manfred Nowak <svv1999 hotmail.com> writes:
Scott wrote


 Whats the correct way to use imports


The correct ways in the given case are at least

- to compile by `dmd mat3 main'
- to change the import declaration in "main.d" so that
  `mat3' is imported before `vec3'
- to change the position of the import declaration in "vec3.d" so
that it follows lexically the definition of type `Vec3' 

All these ways enable the compiler to destroy the cyclic importing
in the given case. 

But according to the specs the compiler is indeed buggy.
The specs say:
| The order in which ImportDeclarations occur has no significance.

With your slightly modified example the compiler continues to emit
errors if the import declaration `import vec3, mat3, quat;' is
changed to
import vec3;
import mat3;
import quat;

But the error vanishes on changing the order to
import mat3;
import vec3;
import quat;

This is the proof that the order indeed has a significance for the 
compiler.

-manfred
May 18 2007